Process of refining salt.



C. GLASER & G. J. MULLER.

PROCESS 0F REPINING SALT.

APPLICATION FILED Nov.17, 1909.

Patented May 10, 1910.`

CHARLES GLASER AND GEORGE J'. MULLER, OF BALTIMORE, MARYLAND.

PROCESS OF REEINING SALT.

Specification of Letters Patent.

Patented May im, 11910.

Original application iiled May 17, 1909, Serial No. 496,525. Divided and this application filed November 17, 1909. Serial No. 528,566.

Toy all whom it may concern: Y Be it known that we, CHARLES GLAsEn and GEORGE J. MULLER, citizens of the United y States, and residents of Baltimore, in the ing had to the accompanying drawing,

'filtrate obtained from the which is a schematic representation of one illustrative method of putting the invention into effect. l

This invention relates to the separation from salt (sodium chlorid) of the impurities. which occur with'it in nature and particularly those impurities with which it is generally sold in crude state, prior to refining.` l

This application' is'a division of our application filed May 17, 1909, Serial No. 496,525. l

The object of the invention is to remove the impurities from the salt either absolutely as when the salt is desired for chemical or pathological purposes, where even a fractional percentage of impurity is undesirable; or' to reduce the proportion of im purities to such an extent or leave them only of such character as will make them wholly unobjectionable for ordinary commercial purposes; and to attain these results in a simple and eiiicient manner and at a moderate cost. i

The present invention consists primarily in purifying salt in solid state by leaching it with a solvent which consists of a saturated solution of pure salt containing acid of such character and restricted quantity as to dissolve certain impurities insoluble in water and thusmake them amenable to further treatment and removal; the pure salt solution being obtained from any suitable source and by any suitable process, but preferably by the process described in the application of which this case is a division.

A further feature consists in treating the leaching process referred to and purifying it, 'preferably by the process forming Jthe subject matter of the application of which this is a division, and thereafter reacidulating the resultant puriiied brine and a ain using it for the leaching process -alrea y referred to.

In carrying out the invention, salt in solid form is placed in a suitable vat jor container. A. suitable quantity of saturated solution of substantially pure salt is then treated by the addition of from one to four percent. of hydrochloric acid. With the resultant solution, the salt to be purified is leached. The acid is not suilicient to precipitate any of the salt in the solution, but is su'licient to render soluble the impurities occurring in the salt and make them amenable to the solvent of pure brine, which, after thorough mixing with the salt, may be drawn off in the usual way. The leaching solvent may be reused several times before becoming suiliciently saturatedwith impurities as to render it ine'ective. Or a series of containers of salt may be successively treated by successive charges of solvent and the solvent after being used for such number of times or passed through such number of salt receptacles as may seem advisable, may be subjected to the purifying process by chemical reaction such as described in the application of which the .present case is aY division, and thus made ready for reacidulation and reuse.

To explain the invention more fully, an illustratlve process will be described.

100() kilograms of commercial table salt are placed in a suitable leaching tank, provided with a filtering bottom. To 1000 k of purified brine 10 to 40 kg. of muriatxc acid are added in a suitable storage tank placed above the leaching tank. Alfter thorough mixing, this. acidulated brine is allowed to run into the leaching tank completely covering the salt therein. It is allowed to stand in contact with the salt for 2 to 6 hours and vis then drawn od and pumped back into the storage tank; 1000 kg. of pure brine solution is now added in portions of 250 kg. at a time, to the salt in the leaching tank, the earlier portions carrying with them the remaining impurities and acid, while thelast portion will pass through as pure brine. The salt is ,now removed from the leaching tank and dried 1n a well known manner. The yield is nearly 100() kg. t

Another example is illustrated in the ,ac-

companying drawing, according to which the salt to be treated is contained in receptacleA, while the leaching brines are divided .into` say four` portions, which are placed in separate receptacles and which may be numbered 1, 2, 3 and 4. The brine contained in receptacle number 1 is now acidulated until it contains about four per cent. of acid. The salt in vat lA is now We claim as neW therein leached by the acidulated brine from receptacle number 1 after Which said brineis returned to said rece tacle number l. The batch of salt in A is then leachedA by the brine from receptacle number 2 Which, having noW taken up some of the residuall acid and the dissolved impurities left in thevsalt from the first leaching brine, is not returned to receptacle number 2 but to receptacle number 1. The salt in A is then leached by brine from receptacle number 3 and as this likewise takes up some residual acid and dissolved impurities, though a much smaller roportion, remaining in the salt, said leaching solution number 3 on leaving the salt, is

passed to receptacle number 2. Finally, the` brine from receptacle number 4, Which is a neutral solution of pure salt, is passed through the salt in vat A and takes up any remaining acid and dissolved impurities. While this last leach passes from vat A as substantially pure brine, it is nevertheless slightly contaminated, and is therefore assed to receptacle number 3 to leave room or fresh' supply in receptacle number 4 Where the brine must always be pure, to secure the best results. Each'batch of salt is similarly treated to the contents of the successive brine receptacles, each portion of brine being advanced toward the first receptacle as it takes up acid and4 impurities dissolved out of the salt contained in leaching tank Aeach portion entering itsparticular receptacle but once until it comes to the first receptacle Where it is used repeatedly until it shows an accumulation of workable impurities when it may be drawn of to receptacle B and regenerated. Whenever receptacle number 1 is emptied for regeneration of its contents, the brine from receptacle number 2 is removed to receptacle number l and-suliicient acid added to it in addition to that with which it has been impregnated While being used as a leaching solution to bring it up to four per cent. In practice the old acid brine which has been transferred from receptacle number l to receptacle B is heated to fifty or' sixty degrees centigrade (50 or 60 C) treated with barium chlorid to precipitate all the sulfuric radical and neutralized preferably either by an alkaline solution or by finely ground earthy carbonates such as dolomite, which permits only the calcium and magnesium impurities to remain; the brine is then treated to a solution of,sodium carbonate and sodium hydroxid to precipitate all the calcium and magnesium as calcium and magnesium carbonate and f hydroxid. The precipitates are now permitted to settle, the brine drawn off to receptacle four Where it is neutralizedv with. hydro-V hlolil'ic acid and used Vas a fresh supply of eac 1. The process of purifying salt which consists in leaching salt with its impurity by an acidulated saturated solution of pure salt, thereby dissolving the impurity from the salt to be purified.

2. The process of purifying salt which consists in leaching salt With its impurity by an acidulated saturated solution of pure salt, thereby dissolvin the impurity from the salt to be purifie and then Washing clean with a saturated solution of pure salt.

3. The process of purifying salt containing a plurality of impurities Which consists in leaching the impure salt by an acidulated saturated solution of pure salt thereby dissolving out the impurities from the salt to be purified and then Washing clean With a saturated solution of pure salt.

4. The process of purifying salt containing a plurality of impurities which consists -in leaching the impure salt by an acidulated saturated solution of pure salt thereby dissolving out the impurities from the salt to be purified and then Washing clean with a saturated solution of pure salt, then adding barium chlorid to the acidulated leaching solution to precipitate the sulfuric radical.

5. The process of purifying salt which consists in leaching the impure salt by an acidulated saturated solution of pure salt to .dissolve out the impurities to be removed Washin clean with a saturated solution o pure sa t, then adding barium chlorid to the acidulated leachin solution to precipitate the sulfuric radica and thereafter neutralizing the acidulated solution.v

`6. The process of purifying salt which consists in leaching the impure salt by an acidulated'saturated solution of pure salt to dissolve out the impurities to be removed, Washing clean with a saturated solution of pure salt, then adding barium chlorid to the acidulated leaching solution to precipitate the sulfuric radical and thereafter neutralizing the acidulated solution and simultaneously precipitating impurities of the acidulated solution.

7.The process of purifying salt, Which consists in leaching the impure salt by an acidulated saturated solution of pure salt, to dissolve out the impurities to be removed, Washing clean with a saturated solution of pure salt, then addingl barium chlorid to the acidulated leaching solution, to precipitate the sulfuric radical, thereafter neutralizing the acidulated solution and simultaneously precipitating the impurities of the solution,

excepting elements of salt which those imdissolve out the impurities, vvashin clean With a saturated solution of pure sa t, then adding barium chlorid -to the acidulated leaching solution to precipitate the sulfuric radical and form more salt, then neutralizing the acidulated solution and simultaneously precipitating therefrom the contained impurities exceptlng` those having an element of salt in their composition, and thereafter adding a reagent composed of elements, one of which combines with the salt producing element of the impurities to produce still more salt, While the remainder combine with the remaining elements of the impurities to iform a precipitate.

9. The process of purifying salt inl continuous operation which consists in leaching impure salt with an acidulated saturated solution of pure salt brine todissolve out the impurities from the salt to Abe puried; Washing clean with a saturated solution of pure salt, then adding barium chlorid to the acidulated leaching solution to precipitate the sulfuric radical and form more salt, then neutralizing the acidulatecl solution thus produced and precipitating elements of impurity other than those containing an element of salt; then treating the residual solutions with reagents to produce still more salt and precipitates containing elements foreign to 'pure salt, and iinally taking the purilied brine and reacidulating it for use as a new solvent.

10. The process of separating from sodium chlorld impurities in the form of 0X- ids of iron and other heavier metals, sulfates ,of alkali and earth metals and chlorids of earth metals, which consists in adding'to the impure salt a solution of purified salt containing hydrochloric acid, digesting, sepa rating liquid from solid, Washlng W1th pure brine, and recovering from the solution by addition of barium chlorid, followed by sodium carbonate and sodium hydroxid the impuritiesI in the form of barium sulfate, ferric hydroxid, carbonate of calcium and magnesium hydroxid and combining the sodium and chlorin elements of the reagents and the impurities to form sodium chlorid in addition to that sou ht to be purified.

The foregoing specication signed at Baltimore this eighth day of October, 1909.

CHARLES GLAsER. cEoRcE .L MULLER. 

